Statistical Characteristics of Total Electron Content Intensifications on Global Ionospheric Maps

Global ionospheric total electron content (TEC) maps exhibit TEC intensifications and depletions of various sizes and shapes. Characterizing key features on TEC maps and understanding their dynamic coupling with external drivers can significantly benefit space weather forecasting. However, comprehensive analysis of ionospheric structuring over decades of TEC maps is currently lacking due to large data volume. We develop feature extraction software based on image processing techniques to extract TEC intensification regions, that is, contiguous regions with sufficiently elevated TEC values than surrounding areas, from global TEC maps. Applying the software to the Jet Propulsion Laboratory Global Ionospheric Map data, we generate a TEC intensification data set for years 2003-2022 and carry out a statistical study on the number and strength of TEC intensifications. We find that the majority of the TEC maps (about 86%) are characterized with one or two intensification(s), while the rest of the TEC maps have three or more intensifications. Both the number and strength of TEC intensifications exhibit semi-annual variation that peaks near equinoxes and dips near solstices, as well as an annual asymmetry with larger values around December solstice compared to June solstice. The number and strength of intensifications increase with enhanced solar extreme-violet irradiance. The strength of intensifications also increases with elevated geomagnetic activity, but the number of intensifications does not. In addition, the number of intensifications is not correlated with the strength of intensifications. The ionosphere is an upper atmospheric layer containing free electrons and ions. The abundance of ionospheric electrons varies from one location to another, creating electron intensification and depletion regions of various sizes and shapes. We develop feature extraction software to identify the electron intensification regions from two-dimensional electron abundance maps and generate a data set of their strengths and locations over two decades. We conduct a statistical study of the data set and find that most maps are with one or two intensification region(s). Maps with three or more intensification regions also occur. The number of intensification regions on a TEC map is modulated by season and solar irradiance. The strength of intensification regions is modulated by season, solar irradiance, and solar activity. Our result advances the knowledge on global ionosphere structuring, which is critical for space-borne navigation and communication. Feature extraction software is applied to generate a total electron content (TEC) intensification data set from global TEC maps spanning 20 yearsOne or two intensification(s) are identified for 86% of the TEC maps, while rest of the TEC maps have three or more intensificationsThe occurrence and strength of TEC intensifications vary with season and solar cycle, and the strength varies with geomagnetic activity